If you follow the link from your profile page, it takes you to the description:
http://www.codeproject.com/script/Membership/Types.aspx?#premium[
^]
Which basically mean that you signed up for Workspaces, either free or paid and were given Premium membership as a result to indicate that. Since they are now closed, and will be removed completely soon, I would expect the Premium indicator to disappear soon too.
You won't be charged, or if you were at some point it should be refunded in due course.